Partially quaternized amino-functional organopolysiloxanes and use thereof in aqueous system on textile substrates are disclosed.
Organopolysiloxanes containing amino groups have long been used as textile finishes. Good and soft hand (hereinafter called softness effects) is achieved on textiles treated therewith. Preference is given to using organopolysiloxanes having the amino-functional group—(CH2)3NH(CH2)2NH2.
Such amino-containing organopolysiloxanes when used in textile finishing are customarily present in the form of aqueous microemulsions whose preparation is described in WO 88/08436 for example. Clear microemulsions are produced by heating a mixture of acid-neutralized amino-containing organopolysiloxane, water and emulsifier. According to the process described in EP-A 0138 192, this goal is achieved by shear emulsification in concentrated form, containing little water, by proceeding from the basic ingredients of amino-containing organopolysiloxane in neutralized form, emulsifier and water.
Advantageous softness effects are obtained with organopolysiloxanes whose amino functions are present in the form of the aminoethylaminopropyl groups mentioned. The morphological molecular structure of this side chain is believed to possess particular affinity for the fibre molecules of the textile substrate by embracing them. This results in the polymer molecule having a specific orientation which is responsible for the good softness. This is indirectly corroborated by the fact that acylation (acetylation) of the outer, primary amino functions has an appreciable adverse effect on the softness of the textile substrates treated therewith, since the different kind of molecular structure no longer permits adequate embracing of the fibre molecules and the associated specific orientation.
The amino-containing organopolysiloxanes described and the organopolysiloxanes containing acylated amino groups are typically present as readily dissociable ammonium salts of organic or inorganic acids when in the form of their microemulsions. At above pH 7, the salts are converted into free bases. In the process, the stability of the microemulsions is reduced by the weaker dissociation in the alkaline region, and this in the case of insufficiently acidified textile material and resultant pH values above 7 leads to coalescence of the microemulsion particles and their floating as oil droplets on the surface of the treatment liquor. As the finishing process continues, the oil droplets can transfer to the textile material or else deposit on the rolls of the treatment assemblies. The textiles become stained with silicone spots which are very difficult or impossible to wash off.
This behaviour in textile finishing is an appreciable disadvantage since very many treatment steps to finish textile substrates are carried out in a strongly alkaline medium. Washing operations carried out with insufficient care may leave residual quantities of alkali on the substrate which are carried into the treatment baths during the subsequent finishing steps. Especially in equipment where the amount of treatment liquor is not very large, as in the case of a padder for example, the pH may in the process very quickly rise to above 9 and lead to the split emulsions mentioned.
A further disadvantage of the amino-functional polysiloxanes identified is a tendency to yellow which can arise at drying temperatures above 120° C. in the case of white and light-coloured textile substrates treated therewith.
The amino-functional polysiloxanes identified are used on all textile substrates in the prior art. Woven and knitted fabrics composed of natural fibres, such as cotton or wool for example, and also of synthetic fibres, such as viscose, polyester, polyamide or polyacrylonitrile for example, are successfully treated with such products on a large scale.
In some cases, it is a rather minor aspect of the finishing effects sought that amino-functional polysiloxanes endow textiles not only with good softness, but simultaneously also with a more or less pronounced, hydrophobic character. However, there are textile applications where hydrophobicity is unwelcome. For instance, towels are expected to have not only a good, fleecy softness but also excellent absorbency to achieve an optimal drying effect. Good absorbency is frequently likewise desired for underwear. Similarly, there are many clothing articles in the sports and out-doors sector, such as bicycling or soccer jerseys for example, where absorbency is a prerequisite for the textile base material as well as good softness. The use of amino-functional polysiloxanes is therefore limited or completely impossible in the cases mentioned.
It is also known that microemulsions of organopolysiloxanes bearing quaternary ammonium groups do not have the disadvantages which have been described with regard to thermal yellowing and with regard to stability in alkaline aqueous dilutions. As described hereinbelow, in some cases it is possible, depending on the method of making used and the composition, to achieve good hydrophilicity combined with good absorbency. Organopolysiloxanes bearing quaternary ammonium groups consequently constitute an improvement over amino-containing organopolysiloxanes with regard to these identified properties. However, the identified advantages of polysiloxanes bearing quaternary ammonium groups have to be weighed against the disadvantage that they, compared with polysiloxanes modified with lateral amino groups exclusively, generate less softness on textiles finished therewith.
Organopolysiloxanes bearing quaternary ammonium groups are known from the literature. Different ways are described to make them, and the quaternary ammonium groups of polysiloxanes obtained can be attached to different positions on the polymer backbone of the polysiloxan chain depending on the particular starting materials used and the methods of making. Lateral, terminal and polymer backbone internal positionings of the functional groups and also mixed forms thereof are possible.
For instance, DE-AS-14 93 384 describes a process for preparing organosiloxane compounds or compound mixtures wherein the corresponding methylhydrogenpolysiloxanes are used as starting materials. The methylhydrogenpolysiloxanes in question are generally equilibrated siloxane mixtures in which the number of methylhydrogensiloxy and dimethylsiloxy units conform to a random distribution. The organosiloxanes having quaternary ammonium groups are prepared in a conventional manner by reacting an epoxysiloxane with dimethylamine and converting the resulting dimethylaminoorganosiloxane with a hydrogen halide or with a methyl halide into the quaternary ammonium compound. The compounds prepared in this way are modified organopolysiloxanes where the quaternary ammonium groups are positioned laterally on the polysiloxan chain. The compounds mentioned are recommended for the water-repellent treatment of, for example, glass or aluminium surfaces.
A further way to prepare organopolysiloxanes having lateral quaternary ammonium groups is described in DE 19 652 524-A1. It involves, for example, aminoethylaminopropyl-containing organopolysiloxanes being reacted with methyl p-toluenesulphonate alkylating agent in the presence of water and suitable emulsifiers to form the corresponding quaternary organopolysiloxanes, a microemulsion forming at the same time. The disadvantage of these preparations is the fact that the softness of textiles finished therewith is less pronounced than that obtained with polysiloxanes modified exclusively with lateral amino groups.
The preparation and use of diquaternary polysiloxanes are described in U.S. Pat. No. 4,891,166. The synthesis is effected by reacting polysiloxanes containing terminal epoxy groups with tertiary amines in such ratios that there is at least one tertiary amino group for every epoxy group and the reaction takes place in the presence of an acid equivalent, based on the nitrogen atoms to be quaternized, at elevated temperature. The quaternary ammonium groups on the resulting diquaternary polysiloxanes are by virtue of this special method of preparation exclusively terminal-positioned. The compounds thus prepared are recommended for use in hair treatment agents and cosmetics. The disadvantage of these preparations, as the Applicant has found, is the fact that textiles treated therewith have a less pronounced softness compared with polysiloxanes modified with exclusively lateral amino groups.
A further way to prepare quaternarily modified organopolysiloxanes is described in DE 37 05 121-A1. In this case, the method of preparation is such that the quaternary ammonium groups are exclusively positioned within the polymer main chain. The method of polymerization involves for example a platinum-catalysed addition of allyl glycidyl ether onto α,ω-hydrogendimethylpolysiloxane and subsequent reaction of the resulting α,ω-diepoxypolysiloxane with a ditertiary alkyldiamine under acidic conditions. Hair care is contemplated as a possible use. Again, the disadvantage of these preparations, as the Applicant has found, is the fact that textiles treated therewith have a less pronounced softness compared with polysiloxanes modified with exclusively lateral amino groups.
WO 02/10259-A1 describes quaternarily modified organopolysiloxanes where the quaternary ammonium groups are likewise positioned within the polymer main chain and have terminal, tertiary amino functions. They are recommended for textile finishing and also for cosmetic formulations.
Further polyquaternary polysiloxane polymers having quaternary groups disposed within the polymer main chain are described in U.S. Pat. No. 4,533,714. They are used in cosmetic formulations for hair treatment.
U.S. Pat. No. 3,207,707 describes the preparation of polymers having nitrogen in the main chain, the nitrogen being present in the form of tertiary amino groups, although no quaternary ammonium groups are formed. The products thus prepared are described inter alia for use as packaging and insulating material.
U.S. Pat. No. 3,033,815 describes the preparation of organopolysiloxanes having laterally disposed amino-functional groups and recommended for use as a size for treating fibres, especially glass fibres.
WO 02/10501-A1 describes organopolysiloxanes for use as softeners having reduced foaming tendency which bear laterally disposed alkylated amino-functional groups.
U.S. Pat. No. 5,039,738 provides another way to prepare organopolysiloxanes having laterally disposed tertiary amino-functional groups. They are said to provide improved resistance to yellowing when used on textile substrates.
FR 1 184 198 A describes organofunctional alkylamino-alkylsilanes and organopolysiloxanes prepared therefrom whose laterally disposed amino-functional groups are present in tertiary form.
Silanes and siloxanes having a terminal quaternary ammonium group are described in GB 1 006 729 as useful for treating glass surfaces.
Cationic organopolysiloxanes are prepared in JP 02/157285-A. Because of only one terminal quaternary group, they have surface-active properties and are used as surfactants.
Cationic siloxane copolymers bearing quaternary ammonium groups in the main chain are described in Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 40, 3570-3578 (2002). They are highly branched and are recommended for use as ion exchangers or in the sanitary sector.